Genetics, Populations, Evolution and Ecosystems Flashcards
Define biotic factors.
Living factors.
Define abiotic factors.
Non-living factors.
State 4 ways in which a biotic factor could be identified.
- Species that compete for resources.
- Species that causes disease or are parasites.
- Species used for food.
- Species that are predators.
Define a niche.
The role of a species within its ecosystem or community - what it eats, where it eats, when it eats. Niches can be biotic or abiotic and niches can be separated by time, location or behaviour.
Define interspecific competition.
Competition between different species. The more similar niches, the more competition.
Define intraspecific competition.
Competition within a species. Animals often have their own territories to reduce this competition but there is usually competition for a mate.
State two ways in which one would estimate a population size through a sample which is representative and when we would use each.
- Quadrat - if environment is stable.
- Transect - if the environment is changing.
How does a quadrat remove bias?
It is random because you assign co-ordinates to the area then use dice or a computer to randomly generate co-ordinates.
What type of sample is a transect and how?
It is a systematic sample because sample needs to be taken regularly along the transect.
What is the process of mark-release-recapture?
For mobile species, a trap it used to capture the organism. They are marked and released back into the population. After a time the trapping is repeated and the number of marked and non-marked are recorded.
What is the equation used to estimate a population of a species through marl-release-recapture.
N = (number marked in the first catch) X (total number in second catch).
(divided by) number of recaptures in second catch.
State seven rules and/or assumptions that need to be followed during marl-release-recapture.
- Random collection.
- Large sample size.
- Ethical treatment.
- No net births/deaths/immigration/emigration.
- Mark - not adding selected pressure.
- Must give time for population to mix before recapture.
- Modern - tagging, DNA sample (unique to organism).
What is primary succession?
The starting point from bare ground of the gradual directional change of community over time?
Why does succession occur?
Due to changing biotic and abiotic factors.
State the stages in the progression of primary succession.
Stage 1: A pioneer species colonise bare ground area, as they are adapted to survive in very hostile abiotic conditions. As organisms die, they decompose by microorganisms, adding humus, which leads to the formation of soil which is less hostile, so the soil becomes richer in minerals over time.
Stage 2: Due to less hostile abiotic conditions, other species colonise this area and out-compete the pioneer species as they grow faster and better, they are more fertile, making area less hostile. This increases biodiversity as overtime different habitats are made for different species.
Stage 3: After a few hundred years, woodlands form, preventing light from reaching the floor, so species that are adapted to lower light intensities will out-compete the existing species. The climax community is the most stable as it has the most different habitats and greatest variety of food sources.
What is secondary succession?
A community is damaged, and soil is left. Plants then colonise.
Define speciation.
The formation of a new species.
When does speciation occur?
Speciation occurs when a population is split into two diverse and isolated populations each with a different gene pool. Overtime, they will become two different species and too diverse to reproduce fertile offspring.
What are the two types of speciation?
- Allopatric.
- Sympatric.
What is allopatric speciation.
Allopatric speciation is geographical isolation, overtime, reproductive isolation.
Describe the process of allopatric speciation.
- A geographical isolation splits population into two.
- This prevents interbreeding between the populations and separate gene pools form.
- Different random mutations occur in each population and different selection pressures act on each population.
- This causes the allelic frequency to change differently in each population, they become more genetically diverse overtime.
- Over time, the two populations become two species (cannot interbreed).
What is sympatric speciation?
Sympatric speciation occurs when a mutation causes reproductive isolation.
Describe the process of sympatric speciation.
- Random mutation within a population causes a reproductive isolation for a few individuals.
- This prevents interbreeding between the populations and separate gene pools form.
- The new population will pass their alleles on to their offspring and the population will rise.
- The two populations are two species (cannot interbreed).
Define locus.
The location of a gene on a chromosome.
